BMW i8 Cold Start Issues, Fix for Rough Running Engine

I have some experience with cars and went through something very similar with my 2018 BMW i3. Also had an issue with my old BMW 3 Series before that. The symptoms you're describing match exactly what I experienced, rough starts, multiple attempts needed, and yeah, that annoying spike in fuel consumption. Turned out it was indeed a faulty injector. Took it to my regular workshop, and they confirmed it after running diagnostics. Had to get the injection valve replaced, set me back about 515 Euro, but it solved the problem completely. Before jumping to conclusions though, could you share: How many miles/kilometers on your i8? Are you getting any error codes? Does it run fine once warmed up? This info would help determine if you're dealing with the same issue I had. These hybrid BMWs can be tricky, but once you sort out the injection system, they run like a dream. Let me know these details, and I might be able to help more specifically! Cheers

Hey, thanks for sharing your experience! My i8 has 16683 KM on it, and it just had its latest service last month. You're right, once it warms up, it runs perfectly smooth. No error codes showing up on the dash either. Interesting that you had similar issues with both your BMWs. That 515 euro fix doesn't sound too bad if it sorts the problem completely. Did your mechanics mention how long the repair took? Also curious if they found any other worn parts while they were checking the injection system? Thanks for the help! James

Glad to help! The repair on my i3 took about 3 hours, most of that time was actually spent on diagnostics to make sure they weren't missing anything else. While they were in there, they noticed the fuel pressure regulator was showing early signs of wear, but it wasn't urgent enough to replace yet. They suggested keeping an eye on it though. The labor wasn't too complex since they've dealt with these issues before. Your mileage is actually pretty similar to what mine was when I had the problem (mine was around 17500 KM). That's typically when these issues start showing up in these models. One thing I forgot to mention, before getting it fixed, I tried using some fuel system cleaner thinking it might help, but it didn't make any difference. Best to just get the injector replaced and be done with it. The improvement in cold starts was immediate, and my fuel consumption went back to normal. If your symptoms are matching mine this closely, I'd say you're probably looking at the same repair. Just make sure to use a workshop that's familiar with hybrid BMWs, these engines need specific knowledge to work on. Keep us posted on what you find out! Cheers

Thanks so much for all the detailed info! This is super helpful, especially knowing about the fuel pressure regulator, I'll definitely have them check that while they're at it. I actually tried a fuel system cleaner too before posting here, and like you said, it didn't do anything. Really good to know I wasn't just wasting my time with that attempt! I've got a specialist BMW workshop nearby that I trust, so I'll book it in with them next week. The 3-hour timeframe helps me plan my day too. The matching symptoms and similar mileage really convince me this is probably the same issue. I'll skip any more DIY attempts and just get it properly fixed. Will definitely update the thread once it's sorted, might help someone else with the same problem down the line. Thanks again for sharing your experience. Really appreciate you taking the time to explain everything in detail! James